The environmental impact of pesticides containing pyrethroids is causing alarm in California where a small aquatic animal, which serves as a sort of canary in the coal mine, is dying off due to soil contaminated by lawn chemicals. And what’s true for California may be true throughout the nation, authorities say.

The U.S. Environmental Protection Agency plans to begin reevaluating the risks of pyrethroid pesticides by 2010, but the California Department of Pesticide Regulation is treating the issue with greater urgency, currently examining more than 600 pyrethroid products. The project began in August 2006 after UC Berkeley professor Donald Weston discovered significant levels of pyrethroids in the sediment of northern California streams.

“We do not yet appreciate the extent of impact of pyrethroids, because there has been no pyrethroid monitoring done in most of the country,” Weston said in an e-mail. “Hopefully, that monitoring will be done over the coming years, and I think it likely we will find impacts in many more locations than are currently known.”

Weston’s research showed that a common indicator of freshwater health, the shrimp-like invertebrate Hyalella azteca, died at an elevated rate when exposed to California sediment samples. The culprit? Residential lawn care products that bind to the soil and get washed into streams. If H. azteca are dying from pyrethroid exposure, it is possible that other aquatic animals, including important food sources for fish, are also being affected, researchers say.

The study set off the largest pesticide review in the California department’s 17-year history. Weston warns that although the investigation is unique to the state, the concerns are not. “The lack of data from the other 49 states should not be interpreted as a lack of environmental impact elsewhere,” he said. “There is no reason to believe the issues are limited only to California.”

There are also questions about the impact these chemicals may have on human health, addressed in the Center’s recent investigation. In response to the Center’s work, the EPA said it would hasten its reevaluation of pyrethroids and their natural counterparts, pyrethrins.

California’s review may ultimately affect such popular pest control products as Ortho Ant-B-Gon Dust, Nix Lice Control Spray, and Scotts Turf Builder with SummerGuard. It could result in more severe label warnings or “restricted” status for certain products, according to the department’s website.

The state’s regulators are collecting and evaluating data on pyrethroids from companies whose products contain the chemicals and the Pyrethroid Working Group, an industry coalition, and anticipate issuing an update on their work in the next few months, according to department spokesman Glenn Brank. A report released in March shows that some portions of the review may take at least another year.

Check out the Center’s project Perils of the New Pesticides, including the latest article, “Worldwide Web of Pesticides.”

Or check out PaperTrail’s other environmental coverage.